Thread: Convert garmin .img pseudo-NT to non-NT? I know it's possible, but how?(SOLVED!!!)

Originally Posted by testlelelala

To be clear, i would add that the XXX header need to be "overwritten" to whatever is at the beginning, and NOT inserted if you "insert" you move the data and loose the original absolute offset position, and it won't work.

Yes, of course. I was doing it by
1) calculating the maximum header size that definitely doesn't overlap the subfile bodies (=max(offset_of_header[i] + header_size[i]))
2) copying the calculated amount of bytes starting from header XXX to offset 0.
Of course, we could do something more subtle like calculating the exact size of header XXX in each case. But it would require knowledge of IMG format much deeper than I have. I'm an absolute IMG-noob, as I said.

The header size is located in the first two bytes of each header.
Example: When you found "GARMIN RGN" before that you see two bytes 7D 00 it means x7D which after conversion to decimal is 125 bytes.
Analog with LBL (xEC-->236 bytes), NET(x64-->100 bytes) and NOD(x3F-->3 bytes)
The only one "odd" is the TRE header that is larger that what you see in the first two bytes, because it could change with copyright info, nevertheless this extra info is not necessary, you could only grab the size that you get from the first two bytes.